From: Andrii Nakryiko <andrii@kernel.org>
To: <dwarves@vger.kernel.org>, <acme@kernel.org>
Cc: <bpf@vger.kernel.org>, Andrii Nakryiko <andrii@kernel.org>
Subject: [PATCH v2 dwarves] btf_loader: handle union forward declaration properly
Date: Thu, 22 Oct 2020 12:51:48 -0700 [thread overview]
Message-ID: <20201022195148.3425366-1-andrii@kernel.org> (raw)
Differentiate between struct and union forwards in BTF. BTF type representing
forward declaration (BTF_KIND_FWD) encodes whether the forward declaration is
for struct or union type by using kflag. So use that kflag to create a proper
internal representation of forward declaration.
Tested with btfdiff on vmlinux:
$ PAHOLE=build/pahole ./btfdiff ~/linux-build/default/vmlinux | wc -l
0
Also tested manually:
$ cat test.c
struct struct_fwd;
union union_fwd;
struct s {
struct struct_fwd *f1;
union union_fwd *f2;
};
int func(struct s *s) {
return !!s->f1 + !!s->f2;
}
$ clang -g -target bpf -c test.c -o test.o
$ bpftool btf dump file test.o | grep fwd_kind
[6] FWD 'struct_fwd' fwd_kind=struct
[8] FWD 'union_fwd' fwd_kind=union
$ build/pahole -F btf test.o
struct s {
struct struct_fwd * f1; /* 0 8 */
union union_fwd * f2; /* 8 8 */
/* size: 16, cachelines: 1, members: 2 */
/* last cacheline: 16 bytes */
};
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
btf_loader.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/btf_loader.c b/btf_loader.c
index 9b5da3a4997a..6ea207ea65b4 100644
--- a/btf_loader.c
+++ b/btf_loader.c
@@ -134,12 +134,13 @@ static struct type *type__new(uint16_t tag, strings_t name, size_t size)
return type;
}
-static struct class *class__new(strings_t name, size_t size)
+static struct class *class__new(strings_t name, size_t size, bool is_union)
{
struct class *class = tag__alloc(sizeof(*class));
+ uint32_t tag = is_union ? DW_TAG_union_type : DW_TAG_structure_type;
if (class != NULL) {
- type__init(&class->type, DW_TAG_structure_type, name, size);
+ type__init(&class->type, tag, name, size);
INIT_LIST_HEAD(&class->vtable);
}
@@ -228,7 +229,7 @@ static int create_members(struct btf_elf *btfe, const struct btf_type *tp,
static int create_new_class(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
{
- struct class *class = class__new(tp->name_off, tp->size);
+ struct class *class = class__new(tp->name_off, tp->size, false);
int member_size = create_members(btfe, tp, &class->type);
if (member_size < 0)
@@ -313,7 +314,7 @@ static int create_new_subroutine_type(struct btf_elf *btfe, const struct btf_typ
static int create_new_forward_decl(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
{
- struct class *fwd = class__new(tp->name_off, 0);
+ struct class *fwd = class__new(tp->name_off, 0, btf_kflag(tp));
if (fwd == NULL)
return -ENOMEM;
--
2.24.1
reply other threads:[~2020-10-22 19:52 UTC|newest]
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